Hot-dip aluminum-coated steel wire

ABSTRACT

A hot-dip aluminum-coated steel wire including a steel wire having a diameter of 0.1 to 0.4 mm on which a plating layer is formed, wherein an elongation at break of the hot-dip aluminum-coated steel wire is 5 to 30%, and a ratio of an average diameter of the steel wire which is taken out from the hot-dip aluminum-coated steel by removing the plating layer per 100 mm in length of the steel wire to the minimum diameter of the steel wire satisfies the formula: [minimum diameter/average diameter]≥[1−(elongation at break (%)/100)], and a method for producing a hot-dip aluminum-coated steel wire including wire-drawing a hot-dip aluminum-coated steel wire so that a ratio of an average diameter of the steel wire which is taken out from the hot-dip aluminum-coated steel by removing the plating layer per 100 mm in length of the steel wire to the minimum diameter of the steel wire satisfies the above-mentioned formula, and an elongation at break of the hot-dip aluminum-coated steel wire is 5 to 30%.

TECHNICAL FIELD

The present invention relates to a hot-dip aluminum-coated steel wire. More specifically, the present invention relates to a hot-dip aluminum-coated steel wire being excellent in twisting property, which can be suitably used in, for example, a wire harness of an automobile and the like, and a method for producing the same.

In the present description, “hot-dip aluminum-coated” used in the term of the hot-dip aluminum-coated steel wire reveals a kind of aluminum plating. The hot-dip aluminum-coated steel wire means a steel wire to which aluminum plating has been applied by dipping a steel wire in molten aluminum, and continuously drawing up the steel wire from the molten aluminum. The twisting property means a property showing that a steel wire is hard to be broken when the steel wire is twisted.

BACKGROUND ART

As an electric wire which is used in a wire harness of an automobile and the like, a twisted wire has been used. The twisted wire has been produced by using hot-dip aluminum plated steel wires produced by applying molten aluminum plating to steel core wires in plural such as 7, 19 or the like, and carrying out twisting of the hot-dip aluminum plated steel wires. When the twisted wire is produced, the hot-dip aluminum-coated steel wires which are to be used in the twisted wire are twisted. When the twist of the hot-dip aluminum-coated steel wires becomes greater, the hot-dip aluminum-coated steel wires come to be broken. Accordingly, an index for preventing the hot-dip aluminum-coated steel wires from torsional breaking has been required.

As a hot-dip aluminum-coated steel wire having improved resistance to twist, there has been proposed a hot-dip aluminum-coated steel wire to which drawing has not been applied after hot-dip aluminum-coating, in which the hot-dip aluminum-coated steel wire has a steel core having a diameter of 0.05 to 0.50 mm as a core material, and an amount of molten aluminum deposited to the hot-dip aluminum-coated steel wire is uniformized so that an average diameter D_(A) (mm) and a minimum diameter D_(MIN) (mm) in its longitudinal direction satisfy the formula (1):

(D _(A) −D _(MIN))/≤0.10   (1)

(see claims 1 and 2 of Patent literature 1). It has been required for the above-mentioned hot-dip aluminum-coated steel wire to satisfy the above-mentioned formula (1), in order to secure torsional resistance showing twisting number of 50 or more at break per 100 mm in length of the hot-dip aluminum-coated steel wire (see paragraph [0022] of Patent literature 1).

PRIOR ART LITERATURES Patent Literatures

Patent literature 1: Japanese patent unexamined publication No. 2014-185355

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In the above-mentioned hot-dip aluminum-coated steel wire, a hard steel wire has been used as an element wire (see paragraph [0034] of Patent literature 1). The elongation of the hard steel wire is approximately 5% or lower. When wire-drawing is applied to the hot-dip aluminum-coated steel wire in which the hard steel wire is used as an element wire, the twisting property is remarkably lowered. Accordingly, the above-mentioned hot-dip aluminum-coated steel wire to which wire-drawing has not been applied has been used (see paragraph [0023] of Patent literature 1).

When molten aluminum plating is applied to a steel wire having an elongation higher than the hard steel wire, such as an austenitic stainless steel wire showing an elongation at break of 30% or more, a twisting number of the resulting hot-dip aluminum-coated steel wire will be several hundred times per 100 mm of a length of the hot-dip aluminum-coated steel wire in many cases, even though the hot-dip aluminum-coated steel wire does not satisfy the relation shown by the above-mentioned formula (1). In addition, the hot-dip aluminum-coated steel wire has a certain degree of twisting property even though wire-drawing has been applied to the hot-dip aluminum-coated steel wire.

In recent years, it has been desired to develop a hot-dip aluminum plated steel wire being excellent in twisting property in applying twisting thereto, in which a steel wire having an elongation higher than the hard steel wire is used as an element wire, and to which wire-drawing is applied.

The present invention has been made in view of the above-mentioned prior art, and an object according to the present invention is to provide a hot-dip aluminum-coated steel wire being excellent in twisting property in applying twisting thereto, and a method for producing the same.

Means for Solving the Problems

The present invention relates to:

-   (1) a hot-dip aluminum-coated steel wire including a steel wire     having a diameter of 0.1 to 0.4 mm, on which a plating layer is     formed, wherein an elongation at break of the hot-dip     aluminum-coated steel wire is 5 to 30%, and a ratio of an average     diameter of the steel wire which is taken out from the hot-dip     aluminum-coated steel by removing the plating layer per 100 mm in     length of the steel wire to the minimum diameter of the steel wire     satisfies the formula (I):

[minimum diameter/average diameter]≥[1−(elongation at break (%)/100)]  (I);

and

-   (2) a method for producing a hot-dip aluminum-coated steel wire     including a steel wire having a diameter of 0.1 to 0.4 min, on which     a plating layer is formed, which includes wire-drawing a hot-dip     aluminum-coated steel wire so that an elongation at break of the     hot-dip aluminum-coated steel wire is 5 to 30%, and a ratio of an     average diameter of the steel wire which is taken out from the     hot-dip aluminum-coated steel by removing the plating layer per 100     mm in length of the steel wire to the minimum diameter of the steel     wire satisfies the formula (I):

[minimum diameter/average diameter]≥[1−(elongation at break (%)/100)]  (I).

Effects of the Invention

According to the present invention, a hot-dip aluminum-coated steel wire being excellent in twisting property in applying twisting thereto, and a method for producing the same are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic explanatory view showing one embodiment for producing a hot-dip aluminum-coated steel wire according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a boundary between a steel wire and a surface of molten aluminum when the steel wire is drawn up from the molten aluminum in producing the hot-dip aluminum-coated steel wire according to the present invention.

FIG. 3 is a schematic explanatory view showing an apparatus for evaluating twisting property of a hot-dip aluminum-coated steel wire used in each of working examples according to the present invention and each of comparative examples.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a method for producing a hot-dip aluminum-coated steel wire according to the present invention will be described based on drawings. However, the present invention is not limited only to the embodiments shown in the drawings.

FIG. 1 is a schematic explanatory view showing one embodiment for producing a hot-dip aluminum-coated steel wire according to the present invention. FIG. 2 is a schematic cross-sectional view showing a boundary between a steel wire and a surface of molten aluminum when the steel wire is drawn up from the molten aluminum in producing the hot-dip aluminum-coated steel wire according to the present invention.

According to the present invention, a hot-dip aluminum-coated steel wire 3 can be produced by dipping a steel wire 2 in molten aluminum 1, and thereafter continuously drawing up the resulting hot-dip aluminum-coated steel wire 3 from the molten aluminum 1.

The steel material which constitutes the steel wire 2 includes, for example, stainless steel, mild steel and the like, and the present invention is not limited only to those exemplified ones.

The stainless steel is an alloy steel containing 10% by mass or more of chromium (Cr). The stainless steel includes, for example, austenitic stainless steel, ferritic stainless steel and martensitic stainless steel, which are specified in JIS G4309, and the like, and the present invention is not limited only to those exemplified ones. Specific examples of the stainless steel include a stainless steel in which an austenite phase is quasi-stable, such as SUS301 and SUS 304; stable austenite stainless steel such as SUS305, SUS310 and SUS316; ferritic stainless steel such as SUS405, SUS410L, SUS429, SUS430, SUS434, SUS436, SUS444 and SUS447; martensitic stainless steel such as SUS403, SUS410, SUS416, SUS420, SUS431 and SUS440; chromium.-nickel-manganese-based stainless steel classified into SUS200 series; and the like. The present invention is not limited only to those exemplified ones.

The mild steel includes steel materials specified in the steel wire of JIS G3532, steel materials specified in the standard of the soft steel wire material of JIS G3505 and the like, and the present invention is not limited only to those exemplified ones.

Among the steel materials, the stainless steel is preferable from the viewpoint of enhancement of tensile strength of the hot-dip aluminum-coated steel wire 3.

The diameter of the steel wire 2 before wire-drawing is not particularly limited. It is preferred that the diameter is appropriately adjusted in accordance with uses of the hot-dip aluminum-coated stainless steel wire 3. When the hot-dip aluminum-coated steel wire 3 is employed in, for example, uses such as a wire harness of an automobile, the diameter of the steel wire 2 before wire-drawing is usually 0.2 to 0.4 mm or so.

In FIG. 1, the steel wire 2 is fed out from a delivery device 4 of the steel wire 2, continuously conveyed in the direction of an arrow A, and dipped in molten aluminum 1 of a plating bath 5. The steel wire 2 dipped in the molten aluminum 1 is drawn up from a surface 6 of the molten aluminum 1, and thereby the hot-dip aluminum-coated steel wire 3 in which the molten aluminum 1 is deposited to the surface of the steel wire 2 is obtained.

Since a plating film (plating layer) of the molten aluminum 1 has been formed on the surface of the hot-dip aluminum-coated steel wire 3, the hot-dip aluminum-coated steel wire 3 is excellent in adhesion to an aluminum wire, and also excellent in tensile strength and temporal stability of electric resistance.

In the molten aluminum 1, pure aluminum can be used. Alternatively, other elements can be contained in the molten aluminum 1 as occasion demands within a scope which would not hinder an object of the present invention.

The above-mentioned other elements include, for example, nickel, chromium, zinc, silicon, copper, iron and the like, and the present invention is not limited only to those exemplified ones. When these elements are contained in aluminum, mechanical strength of the plating film can be increased, and tensile strength of the hot-dip aluminum-coated steel wire 3 can be increased. Among the above-mentioned other elements, silicon is preferable from the viewpoint of inhibition of generation of an iron-aluminum alloy layer which imparts brittleness to a boundary between iron contained in the steel wire and aluminum contained in the plating film, which differs depending on the kind of the steel wire, increase in mechanical strength of the plating film, and efficient plating of the steel wire 2 by lowering of the melting point of the molten aluminum 1.

The lower limit of the content of the other elements in the plating film is 0% by weight. The lower limit is preferably 0.3% by mass or more, more preferably 0.5 by mass or more, furthermore preferably 1% by mass or more, from the viewpoint of sufficient expression of properties of the other elements. The upper limit is preferably 50% by mass or less, more preferably 20% by mass or less, and furthermore preferably 15% by mass or less, from the viewpoint of suppression of potential difference corrosion which is caused by contacting the other elements with an aluminum wire used in production of a twisted wire.

The molten aluminum 1 may inevitably contain elements such as Fe, Cr, Ni, Zn and Cu.

When the steel wire 2 is drawn up from the molten aluminum 1, it is preferred that the steel wire 2 is contacted with a stabilization member 7 at the boundary between the steel wire 2 and the surface 6 of the molten aluminum 1 as shown in FIG. 2.

The stabilizing member 7 includes, for example, a square bar made of stainless steel, the surface of which is wounded by a heat-resistant cloth, and the like. It is preferred that a new surface (surface having not yet been contacted) of the heat-resistant cloth wounded around the stabilizing member 7 is contacted with the steel wire 2 from the viewpoint of suppression of adhesion of a lump of molten aluminum to the surface of the hot-dip aluminum-coated steel wire 3. The new surface (surface having not yet been contacted) of the heat-resistant cloth wounded around the stabilizing member 7 can be formed by, for example, using the stabilizing member 7 on which the heat-resistant cloth has been previously wounded., and sequentially winding the heat-resistant cloth when the steel wire 2 is drawn up while bringing the stabilizing member 7 into contact with the steel wire 2.

It is preferred that the stabilization member 7 is simultaneously contacted with both of the surface 6 of the molten aluminum 1 and the steel wire 2. When the stabilization member 7 is simultaneously contacted with both of the surface 6 of the molten aluminum 1 and the steel wire 2, pulsation of the surface 6 of the molten aluminum 1 is suppressed, and minute vibration of the steel wire 2 is suppressed when the steel wire 2 is drawn up under the condition that the steel wire 2 is contacted with the stabilization member 7. Thereby the plating film of the molten aluminum 1 can be uniformly formed on the surface of the steel wire 2. When the stabilization member 7 is contacted with the steel wire 2, the stabilization member 7 can be lightly pressed to the steel wire 2 in order to apply tension to the steel wire 2 as occasion demands from the viewpoint of suppression of minute vibration of the steel wire 2.

In the embodiment shown in FIG. 1, a nozzle 8 for spraying an inert gas toward a boundary between the steel wire 2 and the surface 6 of the molten aluminum 1 is provided. The inert gas can be supplied, for example, from a device 9 for supplying an inert gas through a pipe 10 to the nozzle 8. The device 9 for supplying an inert gas or the pipe 10 can be provided with a flow rate control device (not shown in the figure) such as a valve in order to control a flow rate of the inert gas.

In the present invention, a distance from the steel wire to a tip 8 a of the nozzle 8 (shortest distance) and a temperature of the inert gas which is discharged from the tip 8 a of the nozzle 8 are appropriately controlled, and an inner diameter of the tip 8 a of the nozzle 8 and a volume flow rate of the inert gas which is discharged from the nozzle 8 are appropriately controlled, so that the hot-dip aluminum-coated steel wire 3 having an even diameter, on the surface of which the lump of molten aluminum is hardly deposited can be efficiently produced.

The inner diameter of the tip 8 a of the nozzle 8 is preferably 1 mm or more, more preferably 2 mm or more, from the viewpoint of efficient production of the hot-dip aluminum-coated steel wire 3 by exactly spraying the inert gas which is discharged from the tip 8 a of the nozzle 8 to the boundary between the steel wire 2 and the surface 6 of the molten aluminum 1. The inner diameter is preferably 15 mm or less, more preferably 10 mm or less, and still more preferably 5 mm or less, from the viewpoint of production of the hot-dip aluminum-coated steel wire 3 having an even diameter, on the surface of which the lump of molten aluminum is hardly deposited.

The distance from the steel wire 2 to the tip 8 a of the nozzle 8 (shortest distance) is preferably 1 mm or more from viewpoint of avoidance of contact of the tip 8 a with the steel wire 2, and efficient production of the hot-dip aluminum-coated steel wire 3. The shortest distance is preferably 50 mm or less, more preferably 40 mm or less, still more preferably 30 mm or less, and still furthermore preferably 10 mm or less, from the viewpoint of production of the hot-dip aluminum-coated steel wire 3 having an even diameter, on the surface of which the lump of molten aluminum is hardly deposited.

The inert gas means a gas which is inert to the molten aluminum. The inert gas includes, for example, nitrogen gas, argon gas, helium gas and the like, and the present invention is not limited only to those exemplified ones. Among the inert gases, nitrogen gas is preferable. The inert gas may include, for example, oxygen gas, carbon dioxide gas or the like within a scope which would not hinder an object according to the present invention.

The volume flow rate of the inert gas which is discharged from the tip 8 a of the nozzle 8 is preferably 2 L (liter)/min or more, more preferably 5 L/min or more, and furthermore preferably 10 L/min or more, from the viewpoint of production of the hot-dip aluminum-coated steel wire 3 having an even diameter, on the surface of which the lump of molten aluminum is hardly deposited. The volume flow rate is 200 L/min or less, more preferably 150 L/min or less, and furthermore preferably 100 L/min or less, from the viewpoint of suppression of deposition of the lump of molten aluminum to the surface of the molten aluminum plating steel wire 3 due to scattering of the molten aluminum 1.

The temperature of the inert gas which is discharged from the tip 8 a of the nozzle 8 is preferably 200° C. or higher, more preferably 300° C. or higher, and still more preferably 400° C. or higher, from the viewpoint of production of the hot-dip aluminum-coated steel wire 3 having an even diameter, on the surface of which the lump of molten aluminum is hardly deposited. The temperature of the inert gas is preferably 800° C. or lower, more preferably 780° C. or lower, and still more preferably 750° C. or less, since thermal efficiency comes to be lowered when the temperature of the inert gas is excessively high. The temperature of the inert gas which is discharged from the tip 8 a of the nozzle 8 is a temperature as determined by inserting a thermocouple for determining a temperature into the inert gas at a place where the inert gas is discharged from the tip 8 a of the nozzle 8.

The drawing up rate of the hot-dip aluminum-coated steel wire 3 is not particularly limited when the hot-dip aluminum-coated steel wire 3 is drawn up from the surface 6 of the molten aluminum 1. The average thickness of the molten aluminum plating film existing on the surface of the hot-dip aluminum coated steel wire 3 can be controlled by appropriately adjusting the drawing up rate. It is is therefore preferred that the drawing up rate is appropriately controlled in accordance with the average thickness of the molten aluminum plating film.

A cooling device 11 can be provided as occasion demands as shown in FIG. 1, in order to efficiently solidify an aluminum plating film formed on the surface of the hot-dip aluminum-coated steel wire 3 by cooling the hot-dip aluminum-coated steel wire 3 in the course of drawing up of the hot-dip aluminum-coated steel wire 3. When the cooling device 11 is used, the hot-dip aluminum-coated steel wire 3 can be cooled by spraying, for example, gas, liquid mist or the like to the hot-dip aluminum-coated steel wire 3.

The hot-dip aluminum-coated steel wire 3 thus produced can be collected, for example, by means of a winding device 12 or the like.

It is preferred that the average thickness of the molten aluminum plating film existing on the surface of the hot-dip aluminum-coated steel wire 3 is 5 to 10 μm or so from the viewpoint of suppression of exposure of the steel wire 2 used as a substrate to the outside in a twisting process, a caulking process and the like, and increase in mechanical strength per unit wire diameter.

A plating layer can be formed as an intermediate layer between the steel wire 2 of the hot-dip aluminum-coated steel wire 3 and the molten aluminum plating film. The metal for constituting the plating layer includes, for example, zinc, nickel, chromium, an alloy thereof and the like, and the present invention is not limited only to those exemplified ones. The molten aluminum plating film can be formed of only one layer, or plural plating films made of the same or different metals.

The hot-dip aluminum-coated steel wire 3 obtained in the above can be conducted to wire-drawing by using, for example, a die so that a wire diameter thereof is 0.1 to 0.4 mm.

In addition, the elongation at break of the hot-dip aluminum-coated steel wire 3 is 5% or more, preferably 10% or more, more preferably 15% or more, from the viewpoint of improvement in twisting property of the hot-dip aluminum-coated steel wire 3 after wire-drawing. The elongation at break is 30% or less from the viewpoint of improvement in twisting property of the hot-dip aluminum-coated steel wire 3 after wire-drawing.

The elongation at break of the hot-dip aluminum-coated steel wire 3 is a value as determined based on “Metallic materials-Tensile testing-Method of test at room temperature” defined in JIS 22241 by controlling an original gauge length to 100±1 mm, controlling a distance between grips to 150 mm, and using 9A test piece as described in the column of “Types of a linear or rod-shaped test piece used in a wire or a rod having a diameter or side length of 4 mm or less” of Appendix C of JIS 22241.

In the present invention, a plating layer is removed from the hot-dip aluminum-coated steel wire to give a steel wire, and an average diameter and the minimum diameter of the steel wire per 100 mm in length of the steel wire are determined.

A method for removing the plating layer from the hot-dip aluminum coated steel wire after wire-drawing is not particularly limited. The plating layer can be removed from the hot-dip aluminum-coated steel wire, for example, by dipping the hot-dip aluminum-coated steel wire in 5 to 10% hydrochloric acid having a liquid temperature of room temperature for 10 minutes.

The present inventors have examined elongation of the hot-dip aluminum-coated stainless steel wire after wire-drawing, and influence of variation in the deposited amount of the plating layer on twisting property as to the aluminum-plated stainless steel wire by measuring a wire diameter of the aluminum-plated stainless steel wire after molten aluminum plating, determining the variation of the deposited amount of the plating layer, carrying out wire-drawing of the aluminum-plated stainless steel wire, carrying out a tensile test of the aluminum-plated stainless steel wire to determine an elongation of the aluminum-plated stainless steel wire, and thereafter carrying out a twisting test. As a result, the twisting property of the hot-dip aluminum-coated stainless steel wire has been found to be generally as follows:

(1) Under a condition that the deposition amount of the plating layer is constant, in accordance with increase of the variation in the thickness of the plating layer, the twisting property tends to be lowered,

(2) In accordance with lowering of elongation of the hot-dip aluminum-coated stainless steel wire after wire-drawing, the twisting property tend to be lowered.

Under the condition that the thickness of the plating layer of the hot-dip aluminum-coated stainless steel wire is completely uniform, the minimum diameter of the stainless steel wire of the hot-dip aluminum-coated stainless steel wire is equal to the average diameter of the stainless steel wire. In this case, since the whole of the hot-dip aluminum-coated stainless steel wire is uniformly twisted when the hot-dip aluminum-coated stainless steel wire is twisted, the twisting number becomes maximum.

However, when the hot-dip aluminum-coated stainless steel wire is produced, it is difficult to control the thickness of the plating layer so as to be completely uniform. When the hot-dip aluminum-coated stainless steel wire having a uniform outer diameter is produced by carrying out wire-drawing of a hot-dip aluminum-coated stainless steel wire having an uneven thickness of a plating layer, since an area ratio of the stainless steel to the plating layer after wire-drawing is unchanged from the area ratio of the stainless steel to the plating layer before wire-drawing, the area at the section of the stainless steel wire after wire-drawing relatively becomes smaller than the area at the section of the stainless steel wire before wire-drawing. Accordingly; the wire diameter of the hot-dip aluminum-coated stainless steel becomes relatively smaller in a region where the plating layer of the hot-dip aluminum-coated stainless steel has a larger thickness.

Accordingly, when twisting of the hot-dip aluminum-coated stainless steel wire having an uneven thickness of the plating layer is carried out, the resulting twisted hot-dip aluminum-coated stainless steel wire comes to be broken at a place where the wire diameter of the stainless steel wire is smallest in the twisted hot-dip aluminum-coated stainless steel wire.

The place where the wire diameter of the hot-dip aluminum-coated stainless steel wire is smallest is a place where the thickness of the plating layer is largest. Since the plating layer is formed of aluminum, and the strength of the aluminum is lower than that of the stainless steel, the plating layer hardly contributes to improvement in twisting property.

The present inventors have presumed the twisting number necessary for twisting the hot-dip aluminum-coated stainless steel wire from conditions for twisting the hot-dip aluminum-coated stainless steel wire.

A standard twisting pitch of the twisted hot-dip aluminum-coated stainless steel wire is to be 20 to 40 times of the wire diameter of the hat-dip aluminum-coated stainless steel wire. In other words, one twist is applied to the hot-dip aluminum-coated stainless steel wire by this pitch. It is considered that it is no problem in practical use that the hot-dip aluminum-coated stainless steel wire is not broken when a twist of one rotation is applied to the hot-dip aluminum-coated stainless steel wire at a pitch of 10 times of the wire diameter of the hot-dip aluminum-coated stainless steel wire, in order to prevent the hot-dip aluminum-coated stainless steel wire from break when the hot-dip aluminum-coated stainless steel wire is twisted, and this standard is considered to satisfy acceptance standard.

Accordingly, for example, when the wire diameter of the hot-dip aluminum-coated stainless steel wire is 0.2 mm, in case the steel wire of the hot-dip aluminum-coated stainless steel wire is not broken after twisting of 50 times or more per 100 mm of the hot-dip aluminum-coated stainless steel wire in length, the hot-dip aluminum-coated stainless steel wire satisfies acceptance standard. When the wire diameter of the hot-dip aluminum-coated stainless steel wire is 0.32 mm, in case the steel wire of the hot-dip aluminum-coated stainless steel wire is not broken after twisting of 32 times or more per 100 mm of the hot-dip aluminum.-coated stainless steel wire in length, the hot-dip aluminum-coated stainless steel wire satisfies acceptance standard.

Under the above-mentioned acceptance standard, a relation between variation of the deposited amount of the plating layer of the hot-dip aluminum-coated stainless steel wire and elongation at break of the hot-dip aluminum-coated stainless steel wire after wire-drawing has been examined.

As a result, when a relation between the minimum wire diameter of the stainless steel which is taken out from the hot-dip aluminum-coated stainless steel wire after wire-drawing by removing the plating layer/average of the wire diameters of the stainless steel wire, and the elongation of the hot-dip aluminum-coated stainless steel wire satisfies the formula (I):

[minimum diameter/average diameter]≥[1−(elongation at break (%)/100)]  (I),

it has been found that the hot-dip aluminum-coated stainless steel wire after wire-drawing is not broken when the hot-dip aluminum-coated stainless steel wire after wire-drawing is twisted at a pitch of 10 times of the wire diameter of the hot-dip aluminum-coated stainless steel wire.

Accordingly in the present invention, since the elongation at break of the hot-dip aluminum-coated steel wire is 5 to 30%, and a ratio of the average diameter of the steel wire which is taken out from the hot-dip aluminum-coated steel by removing the plating layer per 100 mm in length of the steel wire to the minimum diameter of the steel wire satisfies the above-mentioned formula (I), the hot-dip aluminum-coated steel wire is recognized to be excellent in twisting property.

The hot-dip aluminum-coated steel wire according to the present invention can be suitably used, for example, in a wire harness of an automobile and the like.

EXAMPLES

Next, the present invention will be more specifically described based on working examples. However, the present invention is not limited only to those working examples.

Examples 1 to 8 and Comparative examples 1 to 9

A hot-dip aluminum-coated steel wire was produced in accordance with the embodiments as shown in FIG. 1.

As a steel wire, a stainless steel wire made of SUS 304, having a wire diameter before plating as shown in Table 1 and elongation at break as shown in Table 1 was used. The stainless steel wire was preheated in nitrogen gas, and thereafter the stainless steel wire was passed through molten aluminum, and drawn up vertically from the surface of the molten aluminum. A heat-resistant cloth was contacted with a meniscus formed around the steel wire at the place where the stainless steel wire was drawn up from the surface of the molten aluminum, and a heated nitrogen gas was sprayed to the contacting part of the heat-resistant cloth, to stabilize a deposited amount of plating. Incidentally, a passing rate of the stainless steel wire was controlled to 300 m/min.

The wire diameter of the hot-dip aluminum-coated steel wire thus obtained was determined. The wire diameter of the hot-dip aluminum-coated steel wire was determined by using an optical outer diameter measuring instrument manufactured by KEYENCE CORPORATION under the product number of LS-7000, and measuring a wire diameter of the hot-dip aluminum-coated steel wire ten times from the sectional two directions at right angles of the diameter of the steel wire at an interval of 0.08 mm in a length direction. The average of the wire diameters was calculated and regarded as a wire diameter. The wire diameter of the hot-dip aluminum-coated steel wire was shown in the column of “wire diameter after plating” of Table 1.

Next, the hot-dip aluminum-coated steel wire was passed through a die to carry out wire-drawing of the hat-dip aluminum-coated steel wire so that the hot-dip aluminum-coated steel wire had a wire diameter shown in the column of “wire diameter after elongation” of Table 1.

A piece (length: 100 mm) was cut out from the wire-drawn hot-dip aluminum-coated steel wire, and dipped in 10% hydrochloric acid having a liquid temperature of room temperature for 10 minutes to remove the plating layer from the piece in order to take out a stainless steel wire from the piece. The wire diameter of the stainless steel wire was determined in the same manner as described above. The results are shown in the column of “wire diameter of steel wire after wire-drawing” of Table 1.

Next, a tensile test was performed five times to the hot-dip aluminum-coated steel wire having a length of 100 mm obtained in the above, and an average of the elongation at break thereof was calculated and regarded as elongation at break. The results are shown in the column of “elongation at break” of Table 1.

In addition, a twisting test of the hot-dip aluminum-coated steel wire obtained in the above was performed by using an apparatus for evaluating the twisting property of a hot-dip aluminum-coated steel wire shown in FIG. 3. FIG. 3 is a schematic explanatory view showing an apparatus for evaluating the twisting property of a hot-dip aluminum-coated steel wire.

More specifically a test wire 13 of the apparatus for evaluating the twisting property was grasped by chucks 14 a and 14 b, and a distance between the chuck 14 a and the chuck 14 b was set to 100 mm. A load was applied to the test wire 13 by using a weight 17 (mass: 50 g) which was fixed to a truck 16 on a test table 15 so that the test wire 13 was not bent. Next, the chuck 14 b was rotated in the direction of an arrow B, and the number of rotations was counted with an integer. The number of rotations was regarded as the twisting number. The results of the twisting number are listed in the column of “twisting number” of Table 1.

[Evaluation]

The hat-dip aluminum-coated steel wire obtained in each working example and each comparative example was evaluated by confirming whether or not the above-mentioned formula (I) was satisfied. When the hot-dip aluminum-coated steel wire satisfies the above-mentioned formula (I), the mark “0” was described in the column “discriminant” of “twisting property” of Table 1. When the hot-dip aluminum-coated steel wire does not satisfy the above-mentioned formula (I), the mark “×” was described in the column “discriminant” of “twisting property” of Table 1.

In addition, when the actual measurement value of the twisting number is equal to or greater than a target number listed in. Table 1, the twisting property was evaluated as “∘”. When the actual measurement value of the twisting number is lower than the target number listed in Table 1, the twisting property was evaluated as “×”. These results are described in the column “actual measurement value” of “twisting property” of Table 1.

TABLE 1 Wire Wire diameter diameter before Wire diameter after after Wire diameter of steel wire Ratio of minimum plating plating (mm) elongation Elongation after wire-drawing (mm) diameter/average (mm) Maximum Average (mm) at break (%) Minimum Average diameter Ex. 1 0.20 0.234 0.215 0.2 26 0.171 0.186 0.917 Ex. 2 0.20 0.276 0.217 0.2 26 0.145 0.184 0.788 Ex. 3 0.21 0.250 0.231 0.2 15 0.160 0.178 0.924 Ex. 4 0.32 0.348 0.336 0.32 22 0.294 0.304 0.967 Ex. 5 0.32 0.410 0.338 0.32 22 0.250 0.308 0.824 Ex. 6 0.21 0.267 0.231 0.2 15 0.150 0.173 0.866 Ex. 7 0.33 0.350 0.344 0.32 10 0.292 0.298 0.983 Ex. 8 0.33 0.366 0.344 0.32 10 0.280 0.297 0.941 Comp. Ex. 1 0.20 0.296 0.215 0.2 26 0.135 0.186 0.724 Comp. Ex. 2 0.21 0.286 0.231 0.2 15 0.140 0.173 0.809 Comp. Ex. 3 0.22 0.223 0.220 0.2 3 0.179 0.182 0.984 Comp. Ex. 4 0.22 0.235 0.220 0.2 3 0.170 0.182 0.984 Comp. Ex. 5 0.32 0.455 0.338 0.32 22 0.225 0.303 0.743 Comp. Ex. 6 0.33 0.405 0.344 0.32 10 0.263 0.298 0.849 Comp. Ex. 7 0.34 0.360 0.351 0.32 4 0.284 0.292 0.974 Comp. Ex. 8 0.34 0.357 0.350 0.32 4 0.287 0.293 0.981 Comp. Ex. 9 0.34 0.379 0.349 0.32 4 0.270 0.293 0.921 Discriminant Twisting number Twisting property 1-Elongation Actual Actual at break Target measurement measurement (%)/100 number value Discriminant value Ex. 1 0.74 50 241  ∘ ∘ Ex. 2 0.74 50 68 ∘ ∘ Ex. 3 0.85 50 314  ∘ ∘ Ex. 4 0.78 31.3 293  ∘ ∘ Ex. 5 0.78 31.3 106  ∘ ∘ Ex. 6 0.85 50 72 ∘ ∘ Ex. 7 0.90 31.3 74 ∘ ∘ Ex. 8 0.90 31.3 112  ∘ ∘ Comp. Ex. 1 0.74 50 36 x x Comp. Ex. 2 0.85 50 43 x x Comp. Ex. 3 0.97 50 45 ∘ x Comp. Ex. 4 0.97 50 18 x x Comp. Ex. 5 0.78 31.3 21 x x Comp. Ex. 6 0.90 31.3 18 x x Comp. Ex. 7 0.96 31.3 12 ∘ x Comp. Ex. 8 0.96 31.3 20 ∘ x Comp. Ex. 9 0.96 31.3  7 x x

From the results shown in Table 1, it can be seen that according to each of working examples, a wire-drawn hot-dip aluminum-coated steel wire being excellent in twisting property during twisting can be obtained.

INDUSTRIAL APPLICABILITY

The hot-dip aluminum-coated steel wire obtained by the method for producing a hot-dip aluminum-coated steel wire according to the present invention can be suitably used, for example, in a wire harness of an automobile and the like.

DESCRIPTION OF SYMBOLS

1: molten aluminum

2: steel wire

3. hot-dip aluminum-coated steel wire

4: delivery device

5: plating bath

6: surface of molten aluminum

7: stabilization member

8: nozzle

8 a: tip of nozzle

9: device for supplying an inert gas

10: pipe

11: cooling device

12: winding device

13: test wire

14 a: chuck

14 b: chuck

15: test table

16: truck

17: weight 

1. A hot-dip aluminum-coated steel wire comprising a steel wire having a diameter of 0.1 to 0.4 mm, on which a plating layer is formed, wherein an elongation at break of the hot-dip aluminum-coated steel wire is 5 to 30%, and a ratio of an average diameter of the steel wire which is taken out from the hot-dip aluminum-coated steel by removing the plating layer per 100 mm in length of the steel wire to the minimum diameter of the steel wire satisfies the formula (I): [minimum diameter/average diameter]≥[1−(elongation at break (%)/100)]  (I).
 2. A method for producing a hot-dip aluminum-coated steel wire comprising a steel wire having a diameter of 0.1 to 0.4 mm, on which a plating layer is formed, which comprises wire-drawing a hot-dip aluminum-coated steel wire so that an elongation at break of the hot-dip aluminum-coated steel wire is 5 to 30%, and a ratio of an average diameter of the steel wire which is taken out from the hot-dip aluminum-coated steel by removing the plating layer per 100 mm in length of the steel wire to the minimum diameter of the steel wire satisfies the formula (I): [minimum diameter/average diameter]≥[1−(elongation at break (%)/100)]  (I). 